Hello.
My experience, I modelled a DSF using an independent zone for the middle cavity. It is important to model the natural ventilation using the AirFlow network objects to take advantage of a better simulation of the effects of pressure difference between inlet/outlet due to wind effect and temperature rise. Even so, it is very hard to simulate natural ventilation in these types of building elements, specially the air flow. My results were not entirely accurate, and I am still to do some more trials on E+.
One thing you can do to improve your results is 1. create independent zones for the inlet and outlet of the chimney so to introduce the right pressure coefficients of each one of these (experimentaly observed); 2. change the wind pressure coefficients of the outdoor surface side of the chimney so to aproximate your air flow results to the experimental data, and thus obtain a better funcionality. Unfortunately, #2 might be a bit laborous trial and error attempt. As far as the temperature gradient is concerned, you can divide your chimney into several vertical zones, or use the Room Air Models to try to find a good aproximation (note that the larger the gap depth and width is, the less accurate will be the air flow transition between vertical zones).
Pedro.
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: aymericnovel@xxxxxxxxx
Date: Tue, 16 Mar 2010 10:26:57 +0000
Subject: [EnergyPlus_Support] Thermal Chimney modelling method
Dear all,
I am struggeling to know whether or not I did simulate properly a solar chimney. It is in Jerusalem climate.
I first modelled a zone adjacent to the office I want to cool down. I positionned a low opening on the partition wall separating the two zones. This wall is of course composed by a structural part, here concrete, 2.5cm polyurethan board insulation and a black selective metal plate. The outer wall of the chimney is a glazed wall with an upper opening.
Although it seems to work logically, it doesn't match experimental results. Basically it seems it doesn't enhance enough the natural ventilation...
Using this method, I certainly don't take into account the temperature gradient within the thermal chimney, right? Is it more reliable to use the object Zone:ThermalChimney?
Plus, an additional problem I can't explain is that I get some massflow through ceilings although I do not activate infiltration calculations...
If anyone has experience modelling thermal chimney, I would be happy to know more about that!
Thanks a million
Aymeric
I am struggeling to know whether or not I did simulate properly a solar chimney. It is in Jerusalem climate.
I first modelled a zone adjacent to the office I want to cool down. I positionned a low opening on the partition wall separating the two zones. This wall is of course composed by a structural part, here concrete, 2.5cm polyurethan board insulation and a black selective metal plate. The outer wall of the chimney is a glazed wall with an upper opening.
Although it seems to work logically, it doesn't match experimental results. Basically it seems it doesn't enhance enough the natural ventilation.
Using this method, I certainly don't take into account the temperature gradient within the thermal chimney, right? Is it more reliable to use the object Zone:ThermalChimney
Plus, an additional problem I can't explain is that I get some massflow through ceilings although I do not activate infiltration calculations.
If anyone has experience modelling thermal chimney, I would be happy to know more about that!
Thanks a million
Aymeric
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